Despatch Protocol Controller - Manual (Page 12)

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Figure 3. CZO Function in Tune Mode
Calibration Zero Offset
The Calibration Zero Offset (CZO) of Protocol is factory preset and tested for the
specified operating conditions. Special instructions for accessing the tune mode to
change the CZO are referred to in the Appendix of this manual.
The CZO may be useful to make the following small temperature corrections to the
control system.
C
Correction of known sensor calibration errors.
C
Correction of any known steady temperature offset between the heated
work-piece (load) and sensor. This is useful for applications where the sensor
cannot be located exactly at the work-piece.
C
Alignment of temperature indications in a multi-zone/multi-controller application,
e.g., at ambient temperature.
Note that the CZO changes the value of the controlled temperature when used in
closed loop control. The CZO function can be represented by the equations:
Temp Indication (
EF) = Sensor Temp (EF) - CZO% [100 (EF) - Sensor Temp (EF)]
Temp Indication (
EC) = Sensor Temp (EC) - CZO% [38 (EC) - Sensor Temp (EC)]
The CZO function is a straight line pivoted around 100 E F (38EC). Thus, the CZO
functions as an offset and has the ability to change the SLOPE of a temperature range.